There is a product that we use called NILODER. It neutralizes the mousy smell in the quansat and the garage. My dad used to use in the truck, as well to get rid of that cow dropping smell that used to stick to his boots. Don't know if it will get rid of a baked in smell on plastic, but is worth a try. We get it at the farm supply store and co-op.

Sorry about the belated reply, KG in MI, The plastic duct is machine internal. The actual exhaust portion is all steel, 4" heavy exhaust pipe, just as cheap and much better than standard dryer kit flex vent hose.
Adrian